The present invention relates to an interface switching apparatus and a switching control method wherein a plurality of information processing systems (hereinafter referred to as the hosts) having a serial interface capable of dynamic insertion and removal can share at least a peripheral device (hereinafter referred to as the device) having the same serial interface. The present invention also relates to a device which can be shared by a plurality of hosts. The present invention further relates to the interface switching apparatus and the switching control method in which a USB (Universal Serial Bus) is applied to the serial interface.
The use of the USB is extending as a serial interface for connecting the peripheral units (devices) such as a keyboard and a mouse to the information processing systems (hosts).
The USB specification is briefly described in "UNIVERSAL SERIAL BUS SPECIFICATION version 1.0 (Jan. 15, 1996), pp. 27-28, available from the U.S. USB Implementers Forum (URL on internet is http://www.usb.org/).
Each USB host is basically connected with one USB device. The use of a USB hub having the port repeater function, however, makes it possible to connect a plurality of USB devices to each USB host.
In addition to USB, a serial interface called IEEE1394 is finding applications. IEEE1394, like USB, is capable of dynamic insertion and removal and can be added through a hub. The data transfer rate of the USB is about 12 MBits/sec at maximum, whereas IEEE1394 specified by IEEE has a data transfer rate as high as 400 MBits/sec.
In recent years, a system called "a cluster" is extending as a system for improving the reliability of information processing systems, in which each of a plurality of information processing systems monitors the operations of the other information processing systems and is ready to switch various processes to a normal system in case of a fault. The cluster system is configured of a plurality of servers, and in order to reduce the installation space, the devices such as the monitors, the keyboards and the mice (hereinafter referred to as "the console devices") are desirably shared in use.
Conventional means for sharing the console devices is switching a monitor signal or a keyboard signal by a switch. The journal "ASCII/V, March Issue" published by ASCII in February 1996, p. 192 discloses a keyboard switch for performing a switching operation by depressing a specified combination of keys on the keyboard.